1. Field of the Invention
The present invention relates to an improvement in valve actuating devices of a four-cycle internal combustion engine.
2. Description of the Prior Art
Conventionally as a valve actuating device of a four-cycle internal combustion engine, there has been known, for instance, such type in which a rocker arm shaft is provided on a cam holder which is fixed to the upper side of a cylinder head and a rocker arm is carried rockably on the shaft and is operatively connected at one end thereof with a valve actuating cam and at the other end with an opening and closing valve (an intake or exhaust valve) via an adjuster which is adapted to adjust a valve clearance. See Japanese Patent Application Publication Kokai No. 172409/83.
The above conventional device, however, suffers from the following problems:
1. A rocker arm shaft for carrying a rocker arm, a coil spring, used to hold the arm in place, and the like components must be provided necessitating a large number of parts in the whole structure, which makes the device complicated and of a large size and heavy weight; and
2. A valve clearance adjusting means is provided on the rocker arm and makes large the mass of movable parts of the valve actuating device, which results in a lower followability of the device to a high speed engine operation.